A mobile game developer is using DynamoDB as a data store and a Web Identity Federation for authorization and authentication. Each item in the DynamoDB table contains the attributes for individual user's game data such as user ID, game scores, and top score where the user ID is the partition key. The developer must control user access to specific data items based on their IDs. In doing so, users will only be able to obtain items that they own. Which of the following solutions must be implemented by the developer?